It sounds like a joke looking for a punch line: how do you get a cloud pregnant? But it is not a joke, nor is it a theory espoused by conspiracy nuts. It is real. There is a way to knock up a cloud. What’s more, human beings have been working in the skies over Los Angeles recently to impregnate clouds in the hopes of making it rain. By the rainfall totals from last week’s storms, break out the cigars because they were successful.
Since the start of January, I have noticed a number of planes flying a grid pattern in the skies over L.A. The contrails were clearly visible. This triggered a memory of something I read a while back about cloud seeding.
The work of impregnating clouds begins with a set of nozzles on the wing of an aircraft that, when the clouds and temperature are perfect, spray silver iodide particles into the sky. The water in the clouds sticks to the silver iodide particles which are heavy, and together they fall to the earth as rain and snow. This can increase the yield for a season by five to fifteen percent. The procedure is not without controversy. Many scientists have doubts about cloud seeding effectiveness and others worry it may cause extreme weather. However, more recent research questions those fears.
According to the California Department of Water Resources, cloud seeding could increase rainfall amounts to more than 400,000 acre-feet each year. Considering that one acre-foot can supply an average household for a year, that is a lot of water. They are also part of the scientific community that claims the procedure is harmless.
Is it possible to simply spray silver iodide across the sky and presto, it rains? No. Air temperature, wind currents, and a few good storms on the horizon must be optimal for the procedure to work.
When it works, though, the results can really help in a drought year. In fact, California has used cloud seeding for sixty years. Many water districts now want to use drones to spray the silver iodide to save costs and avoid potential flight safety issues.
What are the long term ramifications of spraying metallic particles that will eventually fall to earth to be part of the air we breathe and the water we drink? Silver iodide is best known for its historical use in photographic film development. It is tremendously sensitive to light, hence its use with film. The chemical also works as an antiseptic. Overall, silver iodide is less toxic than other heavy metals, but its use in cloud seeding remains controversial. When exposed to the chemical in great quantities, human beings can suffer from argyria, a disease that is not particularly fatal but results in the skin turning blue or grey, which might take some explaining to family members and co-workers.
According to several news sources, cloud seeding has indeed been used here in L.A. during January, and may have played a role in the two storms that passed through town at the end of last week. We did need the rain, but cloud seeding also raises some questions beyond the obvious issues of toxicity. If we were to get an overwhelming amount of rain causing flooding and widespread damage across the region, who would be responsible? Cloud seeding is not an exact science; we cannot determine how much silver iodide should be sprayed to create the desired amount of rain. We spray it and hope for the best. Also, could more extreme weather like tornadoes result from the procedure?
We are all grateful, no doubt, for the rain in our drought year, but I remember clearly a commercial that used to air back when I was a kid. In the ad, Dena Dietrich personified Mother Nature, who was upset about how close Chiffon margarine tasted to real butter. In the climax, her anger boils over and we see a flash of lightning and hear a crash of thunder while the actress says, “It’s not nice to fool Mother Nature.” The line became a cultural touchstone. Like many human endeavors over the years, cloud seeding is messing with nature, and from experience, we know how those kinds of things often work out.